JPH09128793A - Optical pickup device and optical waveguide element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical pickup device and an optical waveguide element capable of reducing the size of the optical waveguide element, eliminating the need of a converging mirror and a waveguide lens and improving incident coupling efficiency. SOLUTION: This device is provided with a light source, an objective lens converging light from the light source on a recording carrier and a beam splitter 5 bisecting reflected light from the recording carrier, and is the optical pickup device leading one side reflected convergence light bisected by the beam splitter 5 to a photodetecting element, detecting a servo error signal, leading the other side reflected convergence light to the optical waveguide element 13 and detecting an optical signal. The optical pickup device is provided with a means imparting astigmatism to the convergence light between the beam splitter 5 and the optical waveguide element 13, and the optical waveguide element 13 is provided with a prism coupler and a photodetector. The means imparting the astigmatism, the prism coupler and the photodetector are constituted and arranged respectively so that the first focal line of the convergence light having the astigmatism led to the optical waveguide element comes in an optical waveguide layer surface, and the first focal point comes to a prism end, and the second focal point comes on the photodetector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device and an optical waveguide element used for recording / reproducing information on / from an optical information recording medium (hereinafter referred to as an optical disk), and more specifically, components on the same substrate. The present invention relates to a waveguide integrated type optical pickup device and an optical waveguide element in which the above are integrated.

[0002]

2. Description of the Related Art A waveguide integrated optical pickup device for recording / reproducing information on / from a magneto-optical information recording medium, which is disclosed in JP-A-5-101476, is shown in FIGS.
It will be described based on. This optical pickup device collects light from a light source on an optical disc through a collimator lens and an objective lens, and guides the returned light to an optical waveguide element,
The magneto-optical signal and the focus error signal are detected.

The light emitted from the semiconductor laser 51 is collimated by a collimator lens 52, the collimated light is incident on a prism 53, is reflected by an optical waveguide element 56, and is condensed on an optical disk 55 by an objective lens 54. It
The return light from the optical disk 55 passes through the objective lens 54 again, enters the prism 53, and is coupled to the optical waveguide element 56.

As shown in FIG. 11, the optical waveguide element 56 is coupled to the first optical waveguide A and the first optical waveguide A which have almost the same effective refractive index in TE and TM modes, and has an effective refractive index in TE and TM modes. And a third optical waveguide 61 coupled to the second optical waveguide, and a prism 53 is adhesively fixed on the first optical waveguide.

The light incident on the prism 53 and coupled by the first optical waveguide A is coupled to the second optical waveguide B and divided into two. One of the guided lights is the waveguide condensing element 57a, 5a.
7b and the photodetectors 58a and 58b are incident on the focus error signal detector, and the focus error signal is detected from the guided light. The other guided light is made incident on the magneto-optical signal detecting section including the third optical waveguide 61 and the photo detectors 59 and 60, and the magneto-optical signal is detected from the guided light.

In the prism coupler disclosed in Japanese Patent Application Laid-Open No. 4-28953, an optical waveguide layer 63 is formed on a substrate 62 as shown in FIG.
A third gap layer 64 and a second gap layer 65, which have a lower refractive index than the optical waveguide layer 63, are laminated on the third layer 3. The end surface of the second gap layer 65 is a tapered portion 65a and has an opening 66 of a predetermined width W. This opening 6
A dielectric prism 67 is adhesively fixed onto the surface 6. In such a configuration, the parallel light incident on the dielectric prism 67 is coupled to the optical waveguide layer 63 via the first gap layer 64. In this conventional example, an optical coupling efficiency of 80% or more is obtained when parallel light is incident with a beam width of about 1 mm.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the conventional example disclosed in No. 6, an optical waveguide element is arranged between the collimator lens and the objective lens, and the parallel light having a large beam diameter of several mm is prism-coupled. At this time, since the size of the optical waveguide element increases in proportion to the beam diameter, the size of the optical waveguide element also increases.

As the size of the optical waveguide element increases, the propagation length of the guided light becomes longer. This propagation length affects the loss of guided light. In other words, in the optical waveguide, since light is confined in a thin film with a thickness of 1 μm or less, guided light is scattered due to the presence of minute irregularities at the thin film interface and the presence of dust on the optical waveguide, and the loss is 1 to 10 dB / cm It has reached. For example, when the propagation loss of the optical waveguide is 10 dB / cm, the propagation efficiency is 80% at the propagation distance of 1 mm, but the propagation efficiency is 10% at the propagation distance of 10 mm, and the light utilization efficiency is greatly reduced. Therefore, it is desired to reduce the size of the optical waveguide device.

Further, in this conventional example, a magneto-optical (MO) signal and a focus servo error signal (Fo) are output from the optical waveguide element.
The signal is detected. However, in such a configuration in which both signals are detected from the optical waveguide element, there is a problem that sufficient signal quality cannot be ensured.

Further, in the case of detecting a focus error signal or the like as shown in the conventional example, a condenser mirror or a waveguide lens for converting parallel light into focused light is required. However, the condensing mirror has to be manufactured by digging the optical waveguide layer deeply, and there is a problem in that the scattering of the guided light due to the roughness of the manufactured etching mirror surface is prevented.

When a waveguide lens is used, there are types such as a mode index type, a diffractive type, and a geodesic type in the waveguide lens. In the mode index type, the effective refractive index of the lens region and the surrounding effective refractive index are Is small, it is difficult to obtain a lens having a small F number, and there is a problem that the focal lengths of the two modes do not match because the effective refractive index of the lens region greatly differs between the TE mode and the TM mode. It was In the diffraction type, it is difficult to obtain high efficiency, and there is a problem that the focal length changes due to the wavelength change. The geodesic type requires a processing accuracy on the order of μm, which is not suitable for mass production.

As described above, the condensing mirror and the waveguide lens have many defects and are not suitable for use in the optical pickup device.

In the conventional example shown in FIGS. 10 and 12, m
Since parallel light with a large beam diameter of the order of m is coupled to the prism coupler, there is a problem that the efficiency of incident coupling to the optical waveguide element fluctuates greatly with variations in the incident angle and wavelength. Therefore, it is necessary to precisely adjust the optical system in order to increase the incident coupling efficiency, and because the allowable range of wavelength fluctuation is narrow, it is possible to stably couple the light of the semiconductor laser whose light source wavelength easily changes due to temperature changes. It was difficult to get it done.

In view of these problems, the present invention provides an optical pickup device and an optical waveguide device in which the size of the optical waveguide device can be reduced, a condenser mirror and a waveguide lens are unnecessary, and the incident coupling efficiency can be improved. The purpose is to do.

[0015]

To achieve the above object, in an optical pickup device of the present invention, a light source, an objective lens for condensing light from the light source on a record carrier, and reflected light from the record carrier are provided. A beam splitter that divides the beam splitter into two is used, and one of the reflected and focused light beams split by the beam splitter is guided to a photodetector to detect a servo error signal,
An optical pickup device for guiding the other reflected focused light to an optical waveguide element to detect an optical signal, wherein the optical pickup device provides astigmatism to the focused light between the beam splitter and the optical waveguide element. And the optical waveguide element includes a prism coupler and a photodetector, and the means for imparting astigmatism, the prism coupler and the photodetector have astigmatism introduced to the optical waveguide element. It is characterized in that the first focal line of the focused light is in the optical waveguide layer surface, the first focus is on the prism end, and the second focus is on the photodetector.

Further, a light source, a collimator lens for converting light from the light source into parallel light, and an objective lens for condensing the parallel light on a record carrier are arranged in this order, and the light source and the collimator lens are arranged. A beam splitter that divides the reflected light from the record carrier into two is provided between the two, and one of the reflected focused lights split by the beam splitter is guided to a photodetection element via a diffraction element to detect a servo error signal. In an optical pickup device that guides the other reflected focused light to an optical waveguide element to detect an optical signal, the optical pickup device imparts astigmatism to the focused light between the beam splitter and the optical waveguide element. Means, the light source, the light detecting element, the means for applying astigmatism and the optical waveguide element are housed in the same package, and the optical waveguide element includes a prism coupler and an optical waveguide. And a means for imparting astigmatism, a prism coupler and a photodetector, wherein the first focal line of the focused light having astigmatism guided to the optical waveguide element is in the optical waveguide layer surface, It is characterized in that one focal point is on the prism end and the second focal point is on the photodetector.

Further, a light source, a collimator lens for converting light from the light source into parallel light, and an objective lens for focusing the parallel light on a record carrier are arranged in this order, and the collimator lens and the objective lens are arranged. And a beam splitter that divides the reflected light from the record carrier into two, and guides one reflected light divided by the beam splitter to a photodetection element through a diffraction element to detect a servo error signal. ,
In an optical pickup device that guides the other reflected light to an optical waveguide element to detect an optical signal, the optical pickup device converts the reflected light into focused light having astigmatism between the beam splitter and the optical waveguide element. The optical waveguide device includes a toric lens for conversion, the optical waveguide device includes a prism coupler and a photodetector, and the astigmatism imparting means, the prism coupler, and the photodetector are non-guided to the optical waveguide device. The first focal line of focused light having point aberration is in the optical waveguide layer surface,
It is characterized in that the first focus is on the prism end and the second focus is on the photodetector.

In the above optical pickup device,
The means for giving the astigmatism is characterized by a cylindrical lens, a diffractive lens, or a flat glass arranged at an angle with respect to the optical axis.

Further, in the optical waveguide element for detecting the optical signal by making the convergent light having astigmatism incident, the optical waveguide element comprises a prism coupler and a photodetector, and the prism coupler and the photodetector. The device is configured such that the first focal line of the focused light having astigmatism guided to the optical waveguide element is in the optical waveguide layer surface, the first focus is on the prism end, and the second focus is on the photodetector. It is characterized by being arranged.

Further, in the optical waveguide element, the means for imparting astigmatism to the light coupled to the optical waveguide element is formed on the light incident surface of the prism coupler. To do.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical pickup device of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing a first embodiment of an optical pickup device of the present invention. This optical pickup device includes a semiconductor laser device 1 as a light source, a grating 3, a hologram 4, a beam splitter 5, an objective lens 7, a photodiode 11, a cylindrical lens 12, and an optical waveguide element 13. Composed. The light 2 emitted from the semiconductor laser device 1 passes through the grating 3 and the hologram 4, passes through the beam splitter 5, and is focused by the objective lens 7 on the magneto-optical disk 8 serving as a record carrier.

The light reflected by the magneto-optical disk 8 is
It again passes through the objective lens 7 and enters the beam splitter 5, where it is split into a servo error signal detection light 9 and a magneto-optical signal detection light 10. Servo error signal detection light 9
Enters the hologram 4 from the beam splitter 5, is diffracted here, is guided to the photodiode 11, and is detected as a servo error signal. On the other hand, the magneto-optical signal detection light 10 has its optical path bent 90 degrees by the beam splitter 5, is converted into light having astigmatism by the cylindrical lens 12, and is guided to the coupler (coupler) portion of the optical waveguide device 13. The light coupled to the optical waveguide in this coupler portion is polarized and separated in the optical waveguide, guided to a photodetector, and detected as a magneto-optical signal.

In the conventional example of FIG. 10 in which an optical waveguide element for detecting a magneto-optical signal is arranged between the objective lens and the collimating lens, parallel light having a large beam diameter on the order of mm is prism-coupled to the optical waveguide. It When parallel light with a large beam diameter is used as incident light to the optical waveguide, the allowable range for incident angle fluctuation and wavelength fluctuation is narrow,
There arises a problem that the size of the optical waveguide element becomes large.
This is because when the incident angle deviates from the optimum incident light, the phase plane of the generated guided light also deviates. Due to

Therefore, in the present invention, these problems are solved by injecting and coupling the focused light to the optical waveguide device. When the focused light is used here, the shift of the phase surface on the incident surface becomes a problem, but at the focus of the focused light, the phase surface is a flat surface, and since it is a plane wave before and after that, the focused light is By aligning the focal point of B with the boundary between the prism and the optical waveguide element, almost the same incident coupling efficiency as in the case where parallel light is coupled with a prism can be obtained.

At this time, since the beam diameter of the focused light coupled to the prism coupler becomes thin, the allowable range of variation of the incident angle is expanded and the incident angle can be easily adjusted. Since the allowable range of wavelength variation is expanded as the beam diameter is smaller, there is no problem when a semiconductor laser is used as a light source. In addition, since the incident coupling efficiency becomes less sensitive to the difference in effective refractive index between the TE mode and the TM mode due to the same effect as the allowable range of the incident angle is expanded, the difference in coupling efficiency between the two modes becomes small. These points are advantageous in a magneto-optical disk pickup device that detects a magneto-optical signal using an optical waveguide element.

For example, in order to obtain a 70% incident coupling efficiency by making parallel light having an incident diameter of 1 mm incident on the prism coupler, the incident angle variation Δθ and the wavelength variation Δλ are Δθ = ± 0.01 ° Δλ = It must be suppressed to a value of ± 0.1 nm. On the other hand, when focused light having a numerical aperture (NA) of 0.17 is incident on the prism coupler, the incident angle fluctuation allowable range Δθ and the wavelength fluctuation allowable range Δλ
Is expanded to Δθ = ± 1 ° Δλ = ± 40 nm.

However, if the focused light is prism-coupled as it is, the guided light spreads in the optical waveguide layer at the same angle as the emission angle of the semiconductor laser light after the coupling. In that case, the light detection surface is widened. However, there is a problem that the length of the optical waveguide cannot be increased in order to suppress the spread.

In the case of using the optical waveguide type polarization mode splitter, if the spread angle of the guided light is larger than the separation angle of the two modes, the polarization separation performance is deteriorated and the magneto-optical signal cannot be obtained. In particular, in order to achieve a high-speed response of the photodetector, it is preferable that the area of the light receiving surface is small, and the spread of guided light must be suppressed as much as possible. Although it is possible to suppress the spread of guided light by providing a condenser mirror or a waveguide lens as described above, these are not suitable for use because of problems such as difficulty in manufacturing and difficulty in obtaining desired characteristics. .

Therefore, in the present invention, astigmatism is imparted to the focused light coupled to the prism coupler, and the two focal points caused by the astigmatism are adjusted to the prism optical waveguide layer boundary and the light receiving surface of the photodetector, respectively. Has been resolved.

This will be described in more detail with reference to FIG. FIG. 2 shows an optical waveguide device 13 having a prism 31 and a polarization separation function, and a cylindrical lens 45.
An optical system combining and is shown. The focused light 32 incident on this optical system passes through the cylindrical lens 45 to become the focused light 46 having astigmatism, and the first focus 37
And a second focal point 38. The distance (astigmatic difference) between the first focus and the second focus is determined by the refractive index and the curvature of the lens.

Of the two focal points, the first focal point 37 having a focal line in the xy plane is adjusted by adjusting the positions of the optical waveguide element and the cylindrical lens 45, and thus the prism 31.
And at the boundary of the optical waveguide layer 39 and at the end of the prism 31. Further, the second focal point 38 having a focal line in the yz plane determines the refractive index and curvature of the lens so as to be located on the light receiving surface of the photodetector.

At this time, at the boundary surface between the prism 31 and the optical waveguide layer 39, the incident light 46 to the prism is condensed in the yz plane, so that the incident light is incident with the same efficiency as that of the incident aberration-free focused light. Light couples into the light guide. The combined light is transmitted to the TE in the polarization splitting unit 33 having a waveguide structure including a layer having a high refractive index.
The mode 34 and the TM mode 35 are separated and focused on the light receiving surface of the photodetector. This light is detected by the photodetector 36, and a magneto-optical signal is obtained.

The input coupling efficiency of this prism coupler is determined by the beam diameter of the incident light beam 46 projected in the propagating direction (z direction) of the guided light and the optical waveguide structure (specifically, between the optical waveguide layer and the prism). The thickness of the layer is almost the same as the thickness of the layer. Therefore, the decrease in the coupling efficiency due to the spread of the incident light beam in the xz plane is slight. Therefore, for example, when an incident light having an NA of 0.17 is made incident, the beam diameter of the incident light beam projected in the z direction can be made as thin as several tens of μm, so that the allowable range of fluctuations in the incident angle and wavelength can be expanded. Moreover, since the beam diameter of the incident light beam is small, the size of the optical waveguide element can be reduced.

After coupling to the optical waveguide, the guided light is focused instead of diverging, so that the focused light is incident on the light receiving surface of the photodetector, and the area of the light receiving surface can be reduced. High-speed response can be achieved. Therefore, it is difficult to manufacture,
The need for a waveguide condensing mirror and a waveguide lens, which had problems in terms of performance, is eliminated.

Since the magnitude of the astigmatic difference can be freely set by changing the curvature of the cylindrical lens, the degree of freedom in designing the optical waveguide increases. Further, even when an optical waveguide type polarization mode splitter utilizing refraction is used, the guided light is focused light, so that mode separation can be performed regardless of the magnitude of the mode separation angle. Particularly in a polarization mode splitter, it is advantageous to reduce the beam diameter of the incident light beam because the difference in the incident coupling efficiency of each polarized light can be reduced.

When astigmatism is generated by using a plano-concave cylindrical lens, the refractive index and curvature of the lens are determined so as to satisfy the following expressions. Here, f ₁ is the distance from the lens to the first focal point, f ₂ is the distance from the lens to the second focal point, and n and r are the refractive index and the curvature of the lens, respectively.

1 / f ₂ = (1-n) / r + 1 / f ₁ According to the above equation, for example, the distance between the first focus and the second focus is 1 m.
If m, the distance from the lens to the first focal point is 1 m
m, the refractive index of the lens is 1.5, and the curvature of the lens is 1 mm.

FIG. 3 is a diagram showing a second embodiment of the optical pickup device of the present invention. Light 2 emitted from a semiconductor laser device 1 as a light source passes through a grating 3 and a hologram 4 and enters a beam splitter 5. The beam splitter 5 is configured by laminating a flat glass 14 and a prism 15, and a polarization selection film 16 is provided in a part between them. A total reflection mirror 17 is provided on the back surface of the flat glass 14.

The light incident on the beam splitter 5 is reflected by the total reflection mirror 17, passes through the collimator lens 6, and is condensed by the objective lens 7 on the magneto-optical disk 8 which is a record carrier. The light reflected by the magneto-optical disk 8 is
It again enters the beam splitter 5 through the objective lens 7 and the collimator lens 6, and is split into two by the polarization selection film 16 into servo error signal detection light and magneto-optical signal detection light 10. The servo error signal detection light enters the hologram 4 from the beam splitter 5, is diffracted here, is guided to the photodiode 11, and is detected as a servo error signal. On the other hand, the magneto-optical signal detection light 10 is given astigmatism by the cylindrical concave lens 18 and guided to the coupler portion of the optical waveguide device 13. The light coupled to the optical waveguide in this coupler portion is polarized and separated in the optical waveguide, guided to a photodetector, and detected as a magneto-optical signal. Since the coupled light to the optical waveguide device 13 has astigmatism, highly efficient and high-performance polarized light separation can be performed.

According to this structure, the cylindrical lens 18, the beam splitter 5, etc. must be arranged and fixed after the semiconductor laser 1 and the optical waveguide device 13 are arranged. At this time, one of the two focal positions changes due to the deviation of the curvature of the cylindrical lens 18 from the design value. However, if the position of the first focal point deviates, the incident coupling efficiency greatly decreases. The axis of the lens should be aligned so that the focal point is not affected by the cylindrical lens.

As a method of generating astigmatism, there are a method using a diffractive lens, a method using a flat glass, etc., in addition to a method using a cylindrical lens.

FIG. 4 shows an optical pickup device in which the cylindrical lens 18 in the optical pickup device of FIG. 3 is replaced with a diffractive lens 19. As the diffractive lens, it is preferable to use a one-dimensional lens such as a Fresnel zone plate type as shown in FIG. This lens becomes a concave lens for the light rays in the xz plane and functions as a flat plate for the light rays in the yz plane, so that astigmatism can be given.

At this time, a diffractive concave lens is used so that the first focus (focus on the side closer to the lens) becomes the focus of the collimating lens. In the diffractive convex lens, the position of the first focal point is displaced by the wavelength variation, and the coupling efficiency of light coupled to the optical waveguide at the first focal point is reduced, so that it is necessary to use a concave lens here.

FIG. 6 is a diagram showing an optical pickup device using flat glass. As shown in FIG. 6, by arranging the flat glass in a tilted manner on the optical path of the focused light incident on the optical waveguide element, astigmatism can be generated in the incident light on the optical waveguide element. The astigmatic difference Δz is expressed by the following equation, where t is the thickness of the flat glass, N is the refractive index, and θ is the angle between the normal to the flat plate and the optical axis.

[0046]

(Equation 1)

Therefore, parameters such as the inclination of the flat glass are determined so that this astigmatic difference Δz is the same as the distance from the prism end to the light receiving surface of the photodetector, and the first focus is the prism end and the second focus is the light. Adjust the element position so that it is located on the light receiving surface of the detector.

FIG. 7 is a diagram showing a third embodiment of the optical pickup device of the present invention. In the optical pickup device of the present embodiment, the beam splitter 5 is provided between the objective lens 7 and the collimator lens 6, and the light reflected by the magneto-optical disk 8 is detected by the beam splitter 5 as the servo error signal detection light 9 And the magneto-optical signal detection light 10 is divided into two, and the optical path of the magneto-optical signal detection light 10 is bent 90 degrees,
The light is focused on the coupler portion of the optical waveguide device 13 by the toric lens.

When the beam splitter is arranged on the optical path of the focused light, the polarization separation characteristic is strongly influenced by the incident angle, and therefore the good polarization separation characteristic cannot be obtained. A toric lens is a lens that has different curvatures in two orthogonal axes. By using this lens, it is possible to convert parallel light into focused light with astigmatism, so place a beam splitter on the optical path of parallel light. It is possible to improve the polarization separation characteristics of the beam splitter.

Next, the optical waveguide device will be described in more detail with reference to FIG. A third dielectric layer 41, a second dielectric layer 40, and a first dielectric layer 39 are formed in this order on the substrate 42. A coupler prism 31 is adhesively fixed on the uppermost first dielectric layer 39.

The coupler prism 31 and the first dielectric layer 3
9. The refractive indices np, n1, n2, and n3 of the second dielectric layer 40 and the third dielectric layer 41 are set so that np>n2> n1 and n3. The layer thickness is set as follows.

[0052]

[Table 1]

When a focused light flux having a beam diameter of several μm is incident on this prism coupler, an incident coupling efficiency of about 80% can be obtained. Also, since the allowable range of incident angle fluctuation and wavelength fluctuation can be expanded, ± 1 ° from the optimum incident angle and ± 40 from the optimum wavelength
A coupling efficiency of 70% can be ensured in the range of nm.
By arranging the cylindrical lens 43 on the optical path of this incident light flux, astigmatism can be given to the focused light, and the spread of the guided light in the optical waveguide layer can be suppressed.

Instead of the cylindrical lens, a diffractive lens, an inclined flat glass plate or the like may be used. When parallel light is incident on the prism coupler, it is possible to convert the parallel light into focused light having astigmatism by disposing a toric lens on the optical path.

FIG. 8 shows an example in which a cylindrical lens is formed on the light incident surface of the prism. Since the cylindrical concave lens 43 imparts astigmatism to the light incident on the optical waveguide element, by using this light, the allowable range of incident angle and wavelength variation can be expanded without reducing the incident coupling efficiency. The guided light can be condensed on the light receiving surface of the photodetector. If the prism is manufactured by means of resin molding or the like, the cylindrical lens can be easily formed on the prism surface, and the optical waveguide element and the cylindrical lens can be integrated so that the number of parts can be reduced.

FIG. 9 is a diagram showing a structure in which a diffractive lens 44 is formed on the light incident surface of the prism in the prism coupler of the optical waveguide device. The incident light to the optical waveguide element is
Since this diffractive concave lens 44 imparts astigmatism, by using this light, the allowable range of incident angle and wavelength fluctuation can be expanded without reducing the incident coupling efficiency, and the guided light can be guided to the light receiving surface of the photodetector. Can be collected. If the prism is manufactured by means of resin molding or the like, the diffractive lens can be easily formed on the prism surface and the optical waveguide element and the diffractive lens can be integrated so that the number of parts can be reduced.

[0057]

According to the optical pickup device of the present invention,
By providing means for imparting astigmatism on the optical path of the incident light of the optical waveguide element and coupling the focused light having astigmatism to the optical waveguide element, the allowable range of incident angle fluctuation and wavelength fluctuation can be expanded. The spread of guided light in the layer can be suppressed. Further, the first focal line of the focused light having the astigmatism is included in the optical waveguide layer, the first focus is on the prism end,
By arranging each component so that the second focal point comes to the photodetector of the optical waveguide device, the allowable values of incident angle fluctuation and wavelength fluctuation can be expanded most effectively, and the spread of guided light can be suppressed. The size of can be reduced.

Further, by arranging the light source, the light detecting element and the optical waveguide element in the same package, the optical pickup device can be downsized.

Further, according to the optical waveguide element of the present invention, the first focal line of focused light having astigmatism is included in the optical waveguide layer, the first focus is at the prism end, and the second focus is at the optical waveguide. By arranging each component so that it comes to the photodetector of the element, it is possible to expand the allowable values of incident angle fluctuation and wavelength fluctuation most effectively
The spread of guided light can be suppressed. In addition, by assembling the means for imparting astigmatism to the detection light integrally with the prism coupler, the number of parts can be reduced and the device can be downsized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of an optical pickup device of the present invention.

FIG. 2 is a diagram showing an optical waveguide device according to the optical pickup device of FIG.

FIG. 3 is a diagram showing a second embodiment of an optical pickup device of the present invention.

FIG. 4 is a diagram showing an optical pickup device using a diffractive lens.

5 is a diagram illustrating a Fresnel zone plate type lens used in the embodiment of FIG.

FIG. 6 is a diagram showing an optical pickup device using flat glass.

FIG. 7 is a diagram showing a third embodiment of the optical pickup device of the present invention.

FIG. 8 is a diagram showing an optical waveguide device manufactured by integrating a means for giving astigmatism and a prism coupler.

FIG. 9 is a diagram showing another example of an optical waveguide device manufactured by integrating a means for giving astigmatism and a prism coupler.

FIG. 10 is a diagram showing a first conventional example.

FIG. 11 is a side view of an optical waveguide device of a first conventional example.

FIG. 12 is a side view showing a second conventional example.

[Explanation of symbols]

 1 semiconductor laser 3 grating 4 hologram 5 beam splitter 6 collimator lens 7 objective lens 8 magneto-optical disk 11 photodetector for servo error signal detection 12 cylindrical lens 13 optical waveguide element 16 polarization selection film 17 total reflection mirror 18 cylindrical lens 19 diffractive lens 20 Flat Glass 21 Toric Lens 31 Prism 36 Photodetector 37 First Focus 38 Second Focus 39 First Dielectric Layer 40 Second Dielectric Layer 41 Third Dielectric Layer 42 Substrate 43 Cylindrical Lens 44 Diffractive Lens

Claims (9)

[Claims] 1. A light source, an objective lens for condensing light from the light source onto a record carrier, and a beam splitter for dividing the reflected light from the record carrier into two, one of which is divided by the beam splitter. In the optical pickup device for guiding the reflected focused light to the photodetector to detect the servo error signal, and for guiding the other reflected focused light to the optical waveguide device to detect the optical signal, the optical pickup device includes: A means for imparting astigmatism to the focused light is provided between the optical waveguide element, the optical waveguide element comprises a prism coupler and a photodetector, the means for imparting astigmatism, prism coupling Device and the photodetector, the first focal line of the focused light having astigmatism guided to the optical waveguide element is in the optical waveguide layer surface, the first focus is on the prism end, and the second focus is on the photodetector. Yeah An optical pickup device characterized by being configured and arranged. 2. The optical pickup device according to claim 1, wherein the means for imparting the astigmatism is a cylindrical lens, a diffractive lens, or a flat glass plate that is arranged inclined with respect to the optical axis. Optical pickup device. 3. The optical pickup device according to claim 2, wherein the refractive index and the curvature of the cylindrical lens are f ₁
Is the distance from the lens to the first focus, f ₂ is the distance from the lens to the second focus, n and r are the refractive indices of the lens,
An optical pickup device characterized by satisfying the following expression in terms of curvature. 1 / f ₂ = (1-n) / r + 1 / f ₁ 4. A light source, a collimator lens that converts light from the light source into parallel light, and an objective lens that focuses the parallel light on a record carrier are arranged in this order, and the light source and the collimator lens are arranged in this order. A beam splitter that divides the reflected light from the record carrier into two is provided between the two, and one of the reflected focused lights split by the beam splitter is guided to a photodetection element via a diffraction element to detect a servo error signal. An optical pickup device that guides the other reflected focused light to an optical waveguide element to detect an optical signal, wherein the optical pickup device imparts astigmatism to the focused light between the beam splitter and the optical waveguide element. A light source, a light detecting element, a means for imparting astigmatism, and an optical waveguide element are housed in the same package, and the optical waveguide element includes a prism coupler and a light detecting element. The astigmatism imparting means, the prism coupler and the photodetector, the first focal line of the convergent light having astigmatism guided to the optical waveguide element in the optical waveguide layer surface, An optical pickup device, characterized in that the focal point is on the prism end and the second focal point is on the photodetector. 5. The optical pickup device according to claim 4, wherein the means for giving the astigmatism is a cylindrical lens, a diffractive lens, or a flat glass plate that is arranged to be inclined with respect to the optical axis. Optical pickup device. 6. A light source, a collimator lens for converting light from the light source into parallel light, and an objective lens for focusing the parallel light on a record carrier are arranged in this order, and the collimator lens and the objective lens are arranged. And a beam splitter that divides the reflected light from the record carrier into two, and guides one reflected light divided by the beam splitter to a photodetection element through a diffraction element to detect a servo error signal. In an optical pickup device for guiding the other reflected light to an optical waveguide element to detect an optical signal, the optical pickup device is configured such that the reflected light is focused light having astigmatism between the beam splitter and the optical waveguide element. And a toric lens for converting the optical waveguide to the optical waveguide device, wherein the optical waveguide device includes a prism coupler and a photodetector, and means for imparting the astigmatism, the prism coupler and the photodetector. Is configured and arranged so that the first focal line of the focused light having astigmatism guided to the optical waveguide element is in the optical waveguide layer surface, the first focus is on the prism end, and the second focus is on the photodetector. An optical pickup device characterized by the following. 7. An optical pickup device comprising a light source, an objective lens for condensing light from the light source onto a record carrier, and an optical waveguide element for detecting an optical signal using reflected focused light from the record carrier. In the optical pickup device, there is a means for imparting astigmatism to the focused light before the optical waveguide element on the optical path, the optical waveguide element includes a prism coupler and a photodetector, The means for imparting astigmatism, the prism coupler and the photodetector, the first focal line of the focused light having astigmatism guided to the optical waveguide element is in the optical waveguide layer surface, the first focus is the prism end, An optical pickup device, characterized in that it is constructed and arranged so that the second focus is on the photodetector. 8. An optical waveguide element for detecting an optical signal by inputting focused light having astigmatism, wherein the optical waveguide element includes a prism coupler and a photodetector, and the prism coupler and the photodetector. The device is configured such that the first focal line of the focused light having astigmatism guided to the optical waveguide element is in the optical waveguide layer surface, the first focus is on the prism end, and the second focus is on the photodetector. An optical waveguide device characterized by being arranged. 9. The optical waveguide element according to claim 8, wherein means for imparting astigmatism to the light coupled to the optical waveguide element is formed on the light incident surface of the prism coupler. An optical waveguide device characterized in that